In audio applications, a speaker may be driven by an amplifier, typically a class AB amplifier. However, class AB amplifiers have low power efficiency. In portable applications, such as cell phones, personal desktop assistants (PDAs), and headphone amplifiers, battery life can be a significant concern. Also, in high-power systems, (e.g. 5 W–300 W), metal heat sinks are typically required because the low efficiency of Class AB amplifiers.
Unlike class AB amplifiers, class D amplifiers have high efficiency. A class D architecture could significantly increase the battery life in portable systems, and could allow multi-channel high-power systems to be designed very light and compact by eliminating the heat sinks that are typically employed. However, when a class D amplifier is included in an integrated circuit (IC), substrate noise and electromagnetic interface (EMI) may both be significant problems.